There has been proposed a technique applicable to a device configured to detect a position of a leading vehicle located ahead of an original vehicle by using multiple sensors, which is configured to determine detection results of object positions by the respective sensors as an identical leading vehicle when the detection results of the object positions are substantially equal to one another in terms of horizontal and front-back directions (see Japanese Patent Application Publication No. 2004-347471). In the case where the detection results by the respective sensors are substantially equal to one another in terms of the horizontal direction but are not substantially equal to one another in terms of the front-back direction, the above-described device determines the object continuously as the identical leading vehicle when velocities of the object detected by the respective sensors are substantially equal to one another, and when detection results on the object by the respective sensors reached the determination that the object was the identical leading vehicle in a previous processing.
However, if another vehicle approaches the leading vehicle detected by the multiple sensors, for example, the other approaching vehicle may be erroneously identified as the object identical to the leading vehicle detected earlier. In this way, the technique described in Patent Literature 1 may not be able to continuously and correctly identify whether or not the object is identical from the detection results on the multiple objects by the multiple sensors.